Expansible hollow core



1967 B. w. SCHWINDT EXPANSIBLE HOLLOW CORE 5 Sheets-Sheet 1 Filed March 18, 1963 FlG.2

INVENTOR.

BENJAMIN SCHWINDT ATTORNEY Jan. 3, 1967 B. w. SCHWINDT 3,296,059 I EXPANSIBLE HOLLOW CORE Filed March 18, 1963 5 Sheets-Sheet 2 FiG.5

I NVEN TOR.

BENJAMIN W. SCH WIND 7' 1957 B. w. SCHWINDT 3,295,959

EXPANS IBLE HOLLOW CORE Filed March 18, 1963 5 Sheets-Sheet 5 BENJAMIN W SCH W/NDT Q BY ATTOQNE Y United States Patent O 3,296,059 EXPANSIBLE HOLLOW CORE Benjamin W. Schwindt, 40 Awixa Ave., Bay Shore, Long Island, NY. 11706 Filed Mar. 18, 1963, Ser. No. 265,935 3 Claims. (Cl. 161-69) This invention relates to hollow-core assemblies and to structural building units including such assemblies as, for example, hollow-core flush veneered doors, hollow-core utility panel units for esthetic appearances or for soundconditioning, light-Weight hollow-core beams, etc.

The structural unit of this invention comprises, generally, a front panel and a rear panel held in parallel spaced relation by a hollow open-core structure which is also secured to the two panels as an integrated unit. In such basic form, the integrated unit may serve as a modular unit to be assembled with other similar units to define a wall structure.

The modular unit may be made in various modifications. Where one panel will not be exposed in service, it may be of any suitable economic material adequate to perform its function. It may be merely to serve as a support for the unit and to hold the other panel in exposed position, where such other panel may be used for its esthetic appearance, or for utility, to serve as a wall facing or the like.

As an example of utilitarian use, the front-facing panel of such a unit may be of absorbent or of reflecting material, relative to sound waves, or to waves generally, such as electromagnetic, including light.

For such or similar service, such modular units may be structurally assembled and disposed in edge-to-edge relation, and the juxtaposed edges appropriately treated for functional or esthetic service by suitable molding.

The internal open-core structure is preferably of planar strip elements. Such planar strip elements may be of any suitable material that will make each strip element self-sustaining, and that will enable the strip to withstand a certain amount of edge-wise pressure. The strip elements will serve both as spacers and as holding elements, and should therefore generaly be of uniform and equal widths.

The invention finds one application to doors of the type defined as hardwood veneered doors. In further defini tion, such doors utilizing this invention are also identified as hollow-core flush veneered doors.

The conventional hollow-core door, of the type involved herein, consists of an internal frame upon which a front panel and a rear panel are suitably mounted to cover both surfaces of the frame and to enclose the space within the frame. Since the area within a frame of such a door may be substantial, it is necessary to provide a filler within theframe space and between the two panels to support the panels in properly spaced relationship, with the two panels in their respective planes and substantially parallel.

Certain requirements of the doors of this kind are specified in the publication entitled Commercial Standard 171-58, available from the Superintendent of Documents at the US. Government Printing Oflice, Washington, DC. and covering or relating to Hardwood Veneered Doors.

One object of the present invention is to provide a door construction that will meet the specifications of that Commercial Standard, and a design that will provide economy in the manufacture of such doors, and to provide a design that will permit the manufacturing operations to be kept within a time limit imposed by the hardening time of the bonding adhesives utilized in certain of the manufacturing operations.

, Another object of the invention is to provide a construction and design of a modular wall unit utilizing a hollow-core between two panels.

Another object of the invention is to provide a design and construction of a light-weight beam utilizing a hollowcore between two side panels that are to serve as beam elements.

Another object of the invention is to provide a design and construction of a modular wall unit with hollow-core construction, to be suitable for use in constructing a curtain wall.

Another object of the invention is to provide a design and construction of a utility wall unit in which panels of various materials may be utilized, such as for absorption or reflection of waves such as sound or light or the like.

In accordance with the present invention, a complete core assembly is formed as a stack of individual strips, all of the same width corresponding to the internal width or spacing between the internal surfaces of the two panels of the structural unit, which take various ultimate forms. Each strip of the stack is held to the next adjacent strip in a manner that will permit the entire stack to be contracted with all of the strips in fiat practically surfaceto-surface engagement between adjacent strips, so the complete core will then be thus contracted and compressed to a minimum dimension like a closed accordion. The strips are held together with adjacent strips by suitable folded elements of self material, or of different material, suitable creased to permit the folds to be pressed flat. With all of the strips thus held in assembly, they may be readily separated like an expanded accordion to a maximum permitted dimension, with each of the folds opening up to a predetermined dimension to define an open space between adjacent strips.

Thus, in accordance with this invention, the hollow core is formed as a contractible and expandable honeycomb type of structure, which may be easily and readily handled in its compressed or contracted condition during various handling operations, and then expanded or opened to a maximum dimension desired for its appropriate placement within the space allocated between the two panels, to provide a series of regularly spaced strips disposed on edge between the inner surfaces of the two surface panels,

to provide both proper spacing for the two surface panels and to serve also as ties between those two panels, since the strips will be glued along their respective edges where they seat against the inner surfaces of those two panels.

One important object of the invention, therefore, is to provide a core that will be simple and economical to make for use as an internal reinforcement between two panels of a modular structural unit, or of a door, or of a beam, or the like. Among many of the time-consuming operations in manufacturing the veneered doors with hollow cores have been those which had to be performed directly at and on the door frames and the panels, in assembling the various kinds of reinforcing core materials on the frames and the panels until each door was completely assembled with both panels in place.

One of the objects and a particular feature of the present invention is the fact that the core structure may be completely prepared and assembled away from the modular structural unit or door and then brought to such structural unit or door and placed in appropriate assembly position in a simple operation that requires a minimum of time.

Since most of the assembly operations require the use and application of bonding adhesive to the several parts being assembled and joined together, it will be readily understood and appreciated how considerable time is saved by the mere operation of placing the entire hollow core assembly with the adhesive applied thereto within 1 the appropriate space in the structural unit, or, for example, within the frame of the door, as distinguished from the conventional operations which require applying adhesive to many separate pieces that are then separately and individually placed in position in assembly on the frame or on the two door side panels.

The construction details of the internal hollow cores, and of the building units in which they are applied, such as doors, utility modular units, and beams, made in accordance with the principles of this invention, are explained in the following specification, taken in connection with the accompanying drawings, in which FIGURE 1 is a perspective view of a hollow veneered door which is to be re-inforced in accordance with the present invention by a hollow core embodying a feature of the present invention;

FIGURE 2 is an internal plan view of the door resting on one panel with the upper panel removed to show the disposition of the hollow core of the present invention as disposed within the frame of the door;

FIGURE 3 is a side elevational and perspective view of a hollow core assembly, embodying the invention, shown in its expanded condition, as might result when the core is permitted to hang freely in suspension from the top strip held to support the core;

FIGURE 4 is a side elevational view of the core assembly of FIGURE 3 in contracted or closed condition with all of the strips in surfac-e-to-surface contact with their adjacent strips;

FIGURE 5 is a perspective view of one long sheet of basic material to be assembled in a stack with other similar sheets of basic material, from which the strips for the internal hollow core will be formed by transverse slicing of the sheets, and shows how a length of folded hinge maternal is glued along each adjacent side edge of such large sheets, for first holding the sheets, and, after the slicing operation, for holding the strips to be cut from such large sheets to constitute the corresponding strips in the core assembly;

FIGURE 5A is a perspective view of a length of folded hinge material that is to be assembled with the sheets of FIGURE 5;

FIGURE 6 is a schematic perspective illustrating how a positioning blade may be utilized to push the material of the hinge fold into the space between two superposed basic sheets to be glued and anchored to those basic sheets, as the pile of sheets is accumulated to the number corresponding to the number of strips that will be needed to make up the core for disposition in a construction unit, such as, for example, the door frame spacing between the two side panels of the door;

FIGURE 7 shows schematically the operation of slitting the pile of sheets, after being formed as shown in FIGURE 6, in order to cut individual sections from the pile of sheets to constitute a core assembly;

FIGURE 8 shows schematically a perspective and end view of a modified arrangement for piling up a stack of basic sheets, with self hinges, from which transverse sections may be cut to serve as hollow core assemblies;

FIGURE 9 is a perspective and end view, similar to the view of FIGURE 8, but showing still another modification of the arrangement for assembling the basic sheets with self material for the hinges and with an internal hinge to permit the use of narrower basic sheets;

FIGURE 10 is a schematic perspective and end view of a paired set of gluing rollers, by means of which a layer of glue may be conveniently and evently applied to both side edges of the core assembly simultaneously while the core assembly is closed in the manner indicated in FIG- URE 4, after which the core assembly may be readily opened in position on a structural unit panel, such as, for example, the door panel, in the manner shown in FIGURE 2, to locate the several strips of the core assembly in their final positions between the structural unit or door panels, ready to receive the upper panel of the structural unit or door which will then engage the upper glued edges of the open core;

FIGURE 11 is a front elevational view of a modular utility unit with a portion of the front panel broken away to expose the inner hollow-core structure between the front and rear panels;

FIGURE 12 is a front end elevational view of the modular unit in FIGURE 11;

FIGURE 13 is a plan view of the modular unit in FIG- URE, 11;

FIGURE 14 is a schematic elevational view of modular utility wall units disposed in edge-to-edge relation, with a suitable molding strip shown to cover the adjacent edges; and

FIGURE 15 is an end elevational view similar to that in FIGURE 12, and showing a double-thickness modular type unit suitable for use as a light-weight beam.

As shown in FIGURE 1, a door 20 of the type considered herein consists generally of two longitudinal side frame elements 22 and 24, called stiles, with two in-between sections or rails 26 and 28 to complete the frame for the door. The stiles and the rails are suitably fastened to each other.

The frame thus formed by the stiles and the rails serves as the basic support for the two panels 32 and 34 that represent the front and the rear panels of the door.

The basic frame of the two stiles and the two rails may also include two lock blocks 36 and 38 shown disposed at appropriate locations directly adjacent each of the stiles 22 and 24. The two lock blocks 36 and 38 are suitably placed adjacent to the two stiles 22 and 24 and to the two face panels 32 and 34.

The space within the frame constituted by the stiles 22 and 24 and the rails 26 and 28, as further defined by the lock blocks 36 and 38, is now to be filled with a suitable supporting arrangement that will serve to space the two side panels 32 and 34 to a flat, parallel and uniform spacing over the entire areas adjacent the open space within the frame including the stiles and the rails and the lock blocks.

A core assembly 40 constructed in accordance with the principles of this invention is shown disposed within the space of the framework in the manner indicated in FIG- URE 2.

Before describing the manner in which the core assembly 40 is formed, brief reference will be made to FIG- URE 3 and FIGURE 4 to illustrate how the core assembly may beexpanded in FIGURE 3 to a maximum. dimension where it will be adequate to fill the space between the top and bottom rails of the door, in the manner shown in FIGURE 2. I

FIGURE 4 shows how the core assembly may be contracted or compressed to a relatively small dimension compared to the expanded distribution of the same core assembly as shown in FIGURE 3.

The procedure for assembling the parts of the door to this stage may be briefly reviewed upon reference to FIG- URE 1.

As may be seen in FIGURE 1, a working table, generally a press plate of metal or wood 45, is employed upon which to form and assemble the door 20. First a panel of the material to be used for the side panel, for example, hardboard, is placed on the table 45 to serve as door panel 32. This panel of hardboard will be wider than the finished panel of the door in order to permit some trimming of the panel 32 to the actual dimension needed.

The bottom and top surfaces of the two stiles 22 and 24 will be adequately covered with a layer of glue and the stiles will then be placed on the hard-board panel 32 in appropriate positions. The two rails 26 and 28 will be similarly covered with a layer of glue on their top and bottom surfaces and then placed in appropriate position on the hardboard between the respective adjacent ends of the two stiles 22 and 24. The two lock blocks 36 and 38 will then be similarly provided with a layer of glue on their bottom and top surfaces and then placed in appropriate position on the hardboard to which the wooden stiles, rails and lock blocks will be bonded by the adhesive as the adhesive hardens. The layer of adhesive in each case will be squeezed out to a minimum thickness as pressure is applied to the doors in the manner that will now be described.

When the panel of hardboard and the frame including the stiles and the rails are assembled, together with the lock blocks, as indicated in FIGURE 1, that assembly is then ready to receive the core filler 40, which is then disposed within the space in the frame as already indicated in FIGURE 2. The top and the bottom edges of the strips of the core 40' will each have been covered with a layer of adhesive, as will be described later in FIGURE 10, which will enable the bottom edges of the strips of core 40 to adhere to the lower hardboard panel 32, and which will enable the top edges of the strips of core 40 to adhere to the top hardboard panel 34 when it is placed in position, as indicated by the dotted outline in FIGURE 1.

Assuming that the core filler 40 has been placed in position within the frame as indicated in FIGURE 2, the top surfaces of the two stiles 22 and 24 and of the two rails 26 and 28 and of the two lock blocks 36 and 38 are covered with a layer of the adhesive to serve to bond those surfaces to the under surface of the top hardboard panel 34.

The top hardboard panel 34, as in the case of the lower hardboard panel 32, will be of appropriate dimensions in excess of the final dimensions desired in the door, for example, about one-eighth of an inch in each direction beyond the final dimensions that will be defined between the parallel outer side surfaces of the stiles and the rails.

The construction of the contractible, expandable core 40 permits the quick glue-applying operation and the quick disposition within the framework space in the door, after which the top panel 34 may be quickly applied.

The construction of the core assembly permits the core assembly 40 to be formed and made entirely separately from the door-assembling operations, and stored within minimum space, to be available for use when needed. Thus, the operation of distributing the core within the door space is a simple operation that requires merely the application of glue to the side edges of the core strips while they are compressed as in FIGURE 4 and then the immediate simple expansion of the core to the space within the door as in FIGURE 2.

Since the adhesive has a setting time of about thirty minutes, a number of doors can be thus assembled within that interval of the setting time of the adhesive. Thus, upon the formation of the one door as indicated in FIG- URE l, as soon as the top panel 34 is placed in appropriate position on the glued top surfaces of the framework and the core assembly 40, the operation of forming a second door may be immediately started by placing a lower panel corresponding to panel 32 on top of the first door, which now serves as a table or base upon which the formation of the second door may proceed.

Experience has dictated and limited the number of doors that may be thus formed and piled, to correspond to approximately forty doors. When a pile of forty doors has been thus assembled, they are rolled as a pile into the space between two jaws of a vertical press, and there pressure is applied to the entire pile of doors for a time interval whose duration is sufiicient to cover the setting time of the adhesive that is used in the operation. Excess adhesive is thus extruded from between engaging surfaces.

The manner in which the core assemblies 40 are made may now be considered.

Since the cores must be expanded to fill the internal space within the frame of the door, and should also be contractible to a minimum space equivalent to merely the total volume of the strips of the core, some suitable holding means must be provided between the respective strips of the core, that will at the same time permit the 6 cores to be contracted to their minimum spacing. Such a device is essentially a hinge.

In this application two types of hinges are disclosed. One type is of a material other than the material of the corrugated board. In another modification, the hinge is essentially part of the corrugated board and is treated to be able to function as a hinge, by the provision of appropriately located score lines, that are already well known in the art for establishing a fold or bend line around which the corrugated board material may be easily and readily bent or folded.

To form the individual core assemblies 40, a number of large basic sheets of corrugated board are first arranged in a stack with appropriate hinge elements disposed between adjacent basic sheets along one pair of opposite side edges.

The manner in which the basic sheets are first arranged in a stack or pile, is illustrated in FIGURE 5. As there shown, a bottom basic sheet is first placed on an appropriate supporting table 102. Two long hinge strips 104 and 106 of folded kraft paper, or of other equivalent tough material, are provided with layers of glue 108 and 109 along their outer longitudinal edge border surfaces to an extent or width 111 sufficient to assure a good bond to the two adjacent corrugated basic sheets 100 and 115. The long folded hinge strip 104 is shown separately in FIGURE 5A. When applied between the two basic sheets 100 and 115, it will be thus glued and secured to those two sheets to serve as a hinge to permit the two sheets 100 and 115 to be placed in substantially close surface-to-surface contact, or to be separated to a distance corresponding to the width of the fold strip 104 between the inner edges of the glued areas 108 and 109.

It is of course immaterial whether the glue is placed first on the sheet 100 or on the fold strip 104, or on both, the important thing being that the fold strip 104 will be placed along the longitudinal edge border of the corrugated sheet 100 to secure one side of the fold'strip 104 to that corrugated sheet. In similar fashion, a second fold strip 106 will be secured to the other side edge border of the corrugated sheet 100.

The second large basic corrugated sheet 115 is then placed on top of the fold strips 104 and 106, after having been appropriately provided with a layer of glue adjacent its two side edges so the sheet will be glued to the two fold strips 104 and 106 along the top areas corresponding to 108 shown on the strip 104.

In similar manner this process is continued, of first applying fold strips such as 104 and 106 on the top basic sheet which is now basic sheet 115, and then a third basic corrugated sheet is placed on the pile with proper gluing between the fold strips and the under surface of the added basic corrugated sheet. I

The number of basic sheets to be thus placed in the pile will be determined by the number of strip elements desired for the complete core assembly shown as 40 in FIGURE 2.

Upon referring for a moment to FIGURE 2, it :will be clear that the strips to be disposed in the transverse space between the two lock blocks 36 and 38 need not be as long as the strips of the core assembly disposed in the space above and below the two lock blocks 36 and 38.

Consequently, when the stack of basic sheets in FIG- URE 5 is assembled, the number of basic sheets in the stack will correspond to the number of strips desired in the core assembly 40, and the widths of the sheets 100, 115, and so forth, should correspond to the lengths of the strips as they will be desired for the core assembly indicated by the core 40 in FIGURE 2. Thus, the bottom basic corrugated sheets that will be piled in the stack to provide the strips in the group of the core 40 of FIGURE 2, will be of the maximum width as indicated for example in FIGURE 5, and the basic sheets that will then be added to the pile or stack in FIGURE 5 corresponding to the middle group of core 40 in FIGURE 2, will be correspondingly narrower and of appropriate width to permit free and easy disposition within the space between the two lock blocks 36 and '38.

Those basic corrugated sheets that will provide the strips 125 of middle group of FIGURE 2, will, of course, be narrower as indicated, .and will be centralized in the stack formed as shown in FIGURE 5. A basic sheet of such narrower width is indicated at 130 in FIGURE and is disposed with its central axis corresponding with the central plane vertically through the central axes of the several sheets 100, 115, and so forth, of the wider dimension.

The hinge elements corresponding to the loop hinge 104 of FIGURE 5A are similarly applied along the longitudinal edges of the narrower basic sheet 130. A number of such narrower basic sheets corresponding to 130 are accumulated in the stack with the folded hinge strips 104 between those basic sheets until the full number of basic sheets is added corresponding to the number of strips needed in the middle group 125 of FIGURE 2.

After the wide basic sheets are placed in the stack on top of the narrower basic sheets 130, to the number desired for the group 122 in FIGURE 2, the stack is complete except for the drying out process of the glue. In order to have this stack of sheets in proper condition, the entire stack will be subjected to sufiicient pressure to assure that the glue will take hold between adjacent matching surfaces, and excess glue squeezed out.

After the glue has dried in the stack of basic sheets under pressure, as assembled and prepared in FIGURE 5, the stack will be contracted to its minimum height, and in this condition will be moved past a suitable saw blade to cut the assembled stack into narrow sections, in which each section will have a width corresponding to the space required within the framework of the door, such as, for example, the space between the inner surfaces of the panels 32 and 34 of a door such as shown on the table in FIGURE 1, or between related panels of modular construction units, beams, or the like.

A stack of strips will be of the form shown in FIGURE 4 when cut from the stack of basic sheets of FIGURE 5. The stack of strips in FIGURE 4, as previously indicated, will constitute the core 40 shown in FIGURE 2, which will correspond to the stack of FIGURE 4 when stretched or opened to its maximum spacing in the manner shown in FIGURE 3.

Thus, by first arranging the long basic sheets in a stack as indicated in FIGURE 5, with the appropriate connecting hinge strips indicated at 104 and 106, the cones as fillers for the doors or other construction units may then be made by the simple operation of slicing them from the stack of basic sheets of FIGURE 5.

As previously explained, and as will now be apparent, the stack shown in FIGURE 5 utilizes two diiferent types of material, that is, the corrugated board representing the sheets 100, 115, 130, and so forth, and the tough paper material represented by the hinge fold 104.

In FIGURE 6 is shown another way in which the stack of FIGURE 5 may be formed. As shown in FIGURE 6, the side edge borders of the basic corrugated double flute sheet 150 are covered with the glue 151 and 152 along the edge borders 153 and 154, and a paper sheet 155 from a roll 160 is pressed into the space above the top of the sheet 150 by a suitable blade 162 supported on a suitable pusher rod 164, the details of which are not necessary here, and the next basic corrugated sheet 170 is placed in position on top of the lower basic sheet 150 with the paper fold 155A between the two corrugated basic sheets 150 and 170. The lower and the upper surfaces of the corrugated basic sheet 170 will be provided with glue along the edge borders, as indicated at the areas 172 and 174. A second hinge fold 155B will then be formed -by the blade 162 pushing in the fold from the paper 155 to the distance desired. Until the paper is pushed in to form the fold hinge 155A or 155B, the paper will normally hang down freely from its roll and will be ready to be pushed inwardly by the blade 162 to form the hinge loop.

The paper roll and the pushing blade 162 are shown on only one side of the pile of basic sheets. A similar roll of paper and a similar blade are provided for the other side of the pile of basic sheets, in order to form the hinge paper loops between the basic corrugated sheets on that side as well.

After the stack of basic corrugated sheets is completed and the glue given time to dry in the assembly of either FIGURE 5 or FIGURE 6, the entire stack thus formed is then subjected to a cutting operation at a suitably disposed band saw or other suitable cutting device 180, as schematically shown in FIGURE 7, to cut a core section from the complete stack of basic corrugated sheets. The core section 185 will correspond to the core assembly 40 shown in FIGURE 2, where the basic corrugated sheets as assembled in FIGURES 5 and 6 have been of the appropriate lwidths to correspond to the respective lengths of the strips shown in the core assembly 40 of FIGURE 2. v.

In the case of the stacks shown in FIGURES 5 and 6, where the hinge material is different from the material of the corrugated boards, and is of a tough thin paper as illustrated in FIGURES 5 and 6, the basic corrugated boards may preferably be of double flute construction in order to provide the desired strength to the individual spacers when they are disposed in the hollow of the frame to space the two door panels.

In order to avoid the necessity of handling two kinds of material, for example, the basic corrugated board, such as the board 100 in FIGURE 5 and then the material of different kinds such as the paper used for the hinge fold 104 of FIGURE 5, a different form of assembly of the basic corrugated sheets may be employed in which only the basic corrugated sheet material is utilized.

As shown in FIGURE 8, basic corrugated board of single flute material may be utilized. A wide sheet 200 is approximately scored to develop and outline a main central body panel 202 and two auxiliary fold-back panels 204 and 206, respectively joined to the main central body panel 202 by hinge panel sections 204A and 204B, on one side, and 206A and 2063 on the other side.

In order to define the two hinge panels 204A and 204B and the back-fold panel 204, suitable score lines will be formed in the original large basic sheet of single flute material at the corners 210, 212 and 214, by suitable means and in the manner well known in the industry, either on only one side or on both sides of the corrugated board, so the two hinge sections 204A and 204B and the fold-back panel 204 can be readily formed by folding. The hinge sections on the other side 206A and 206B and the fold-back panel 206 will be defined by similar score lines appropriately disposed to define and determine the dimensions of the widths of the hinge sections and the dimension of the fold-back panel in each case.

Instarting a stack of the type shown in FIG. 8, it will be seen that the two fold-back panels 204 and 206 will be suitably glued on their outer lower surfaces to be bonded to a starting base panel 220 which also need only be of single-flute material.

It will be observed that the feature of the arrangement shown in FIGURE 8 is that a basic corrugated board of single-flute construction is suitably joined to appropriately disposed panels also of single-flute material in order that together a double-flute structure is formed which provides the appropriate strength wanted in the core spacer strips for spacing and supporting the two spaced panels, such as in a finished door or in a modular construction unit.

As shown in FIGURE 8, after the first box-like structure 221 is formed on the base panel 220, a second structure 222, similar in form and construction to that of 221, may then be disposed on the top of the first box-like structure 221, so that the underfold panels 224 and 226 of the second box assembly will be positioned on and glued to the main or center panel 202 of the first box-like assembly. In similar manner, a complete stack of box-like formations of the single-flute basic corrugated board can be added until the desired number of supporting strips will be provided, at which time a complete core assembly is cut from the stack, similar to the procedure indicated in FIGURE 7.

In FIGURE 9 is shown a modification of the arrangement for forming a stack that is shown in FIGURE 8. In FIGURE 9, a narrower initial basic sheet of single or double-flute material may be utilized. An additional hinge element 230 may be employed, which is glued to the outer surface of a base sheet such as 232 and to the inner surface of the center body panel of the next higher sheet 234. In the arrangement shown in FIGURE 9, all of the material including the main sheet 234, for example, and its two hinge sections 236 and 238, as well as the intermediate hinge element 230, are all of the same material, that is, single or double-flute corrugated board.

Thus, by means of the arrangements and constructions and the procedures disclosed herein, hollow filler cores of wood derivative material, such as corrugated paper board, chip board, etc. may be easily and economically assembled to provide core fillers that can be easily placed in position between the two panels of a door, or of a similar type construction unit, to serve as bonding elements for the two panels involved and as supporting spacer elements to hold the panels in proper spaced position.

An important feature of this invention that provides a substantial advantage in the way of economy, is the fact that the core assemblies, such as indicated at 40 in FIG- URE 2, can all be prepared by work done outside of, and away from, the door or construction unit itself, and such core assemblies can be stored in a minimum of space as inventory, if desired, thereby permitting that operation of preparing the core filler to be accomplished at any appropriate location in the shop, that need not be immediately close to where the doors are being assembled.

This procedure avoids much of the lost time required by previous conventional methods in the performance of which many individual spacers were required to be located in time-consuming operations that were particularly critical because of the drying and hardening time of the glue that is used in the manufacturing of such doors.

The manufacture of such core fillers as taught herein permits the gluing material to be easily and readily applied to the edges of the core assembly in a manner schematically indicated in FIGURE 10.

As shown in FIGURE 10, a gluing assembly 250 is shown as consisting of one pair of rolls 252 to apply glue to one edge of the core assembly, and a second set of rolls 254 to apply glue to the other or lower edge of the core assembly, such as the core assembly 40A of FIGURE 4 shown in contracted condition with all of the strips of the core in substantially surface-to-surface engagement with the adjacent strips.

A core assembly 40A, as shown in FIGURE 4, is moved through the space between the two sets of rollers in FIGURE 10, which rollers are suitably supported to permit them to be spaced to receive and accommodate a core assembly such as 40A of FIGURE 4, of any desired width, depending upon the spacing between the panels of the door or other unit with which the core assembly 40A is to be employed as a spacing and holding medium.

As shown in FIGURE 10, the two sets of rollers 252 and 254 are each provided with batches of glue 256 and 258 which is supplied to the edges of the assembled core 40A simultaneously and immediately before the assembled core is to be positioned, for example, as the core 40 in the door shown in FIGURE 2.

By means of the procedures disclosed herein, the core assemblies can be economically assembled in manufacture and stored until needed for use. The use and provision of the hinge elements, whether of self material or of diflerent material from the corrugated sheet material, enables the core strips to be compacted to minimum space requirements, which is desirable both for storage and for handling, particularly through the gluing operation shown in FIGURE 10. The hinge structure then permits the constructed core assembly after gluing to be stretched from the close coupled arrangement shown in FIGURE 4 to the open spaced arrangement of FIGURE 3. The hinges serve the purpose of holding the strips in proper spacing and in desired parallel relationship in planes transverse to the planes of the door panels, whereby the core strips may perform their functions most effectively, both as holding elements to glue the two door panels together, and as spacing elements to hold the two door panels spaced uniformly throughout the length of the door.

It will be clear that the same core assemblies, of one size, may be used for doors of different heights, by not fully expanding a core assembly for smaller doors.

From the manner in which the core assemblies are prepared and handled and positioned between two panels, it is clear that the use of the core assembly is not limited to a door, with a closed frame of stiles and rails.

The core assembly may be positioned between any two panels, with the border space between the panels otherwise left open. Thus, as in FIGURES 11, 12 and 13, a modular utility structure 300 may be formed as a unit, for use according to the function desired.

The structural unit 300 comprises two panels 302 and 304, held together in spaced relation by the core 306. The core 306 consists of a group of strips 308 of a material that is self sustaining and capable of withstanding a certain amount of edgewise pressure. By means of a suitable adhesive applied to the side edges 310 of the strips 308 where those edges engage the surfaces of the panels, the strips 308 are secured to the two panels 302 and 304 to constitute a rigid structural unit.

The strips 308 are provided with hinge elements 312 between each strip and the next adjacent strip for the purposes previously described in connection with FIG- URES 3 and 4.

The structural unit 300 may be assembled with elements of various kinds. The panels may be of soft or hard woods, or plywoods, or of material of absorbent nature or of reflective nature, relative to sound or light or electromagnetic waves. The structures may be assembled to form curtain walls, or wall coverings, or acoustic ceilings, for example. Thus, one panel may be merely adequate for support and the other of suitable material and surface form and appearance to provide a function and appearance as desired.

The strips may be made of chip board or lath strips. They can then be used with thin plywood panels and provide necessary support and strength for the thin panels.

The use of strips in this manner also permits the utility modular units to be made in any area and size, and in any thickness. Such modular units may be placed edgeto-edge to serve as a wall or ceiling or esthetic space divider. The edges of the front and rear panels need not necessarily be surface-finished where they lie adjacent the edges of next adjacent modular units. The adjacent edges and the spaces between them may be suitably covered by narrow strips 320 of any suitable material and color, preferably opaque, to hide the spaces between adja' cent modular units 300.

The design of the modular unit also permits the construction of a box-type beam, with panels of thin strong material where weight is a factor. The core strips may be disposed in predetermined spacing for necessary reinforcement. Thus, as shown in FIGURES 12 and 15, fillers 340, with strips all of one width, may be positioned between and glued to two thin panels 342 and 344 to hold those two panels together as a rigid structure suitable for use as a beam. In FIGURE 15, for greater strength, a third panel 346 is utilized and held in place by a second strip filler 347. Hinges 349 are indicated in both struc- 1 1 tures. By holding the panels 342, 344 and 346 in vertical position, thefull beam strength of the panels is obtained.

The invention thus discloses a simple construction of core filler for hollow doors and other structures, and simple procedures for forming such filler cores for use in such doors, and other structures.

The invention is not necessarily limited to the exact details of the constructional arrangement shown or of the operational steps for assembling the core elements, since those may be variously modified without departing from the spirit and scope of the invention and its features as disclosed and claimed.

What is claimed is:

1. In combination, a frame having a preselected width and a hollow ladder-type core disposed in said frame, said core comprising a plurality of strips of-corrugated paper board preselected ones of which have a width substantially equal to said preselected width, and hinge-like holding means at the ends of the strips for-holding each strip to an adjacent strip to form a single-cell which extends between the boundaries of said frame, said hinge-like holding means comprising connecting pieces connected between adjacent ones of said strips of corrugated paper board and being foldable alongsaid connections, each of said connecting pieces having a fold line intermediate said connections whereby each connecting piece is foldable along its lines of connection to adjacent ones of said strip and along said intermediate fold line, said connecting pieces being formed of a material that is the same as the corrugated paper board.

2. A hollow ladder-type core, as in claim 1, in which said hinge-like holding means constitute folded extensions of the strips.

3. A hollow ladder-type core, as in claim 1, in which each strip of corrugated paper board consists of a main body and each of said hinge-like holding means consist of a side flap each extending from said main body and each spaced from and held to said main body by a foldable hinge-like intermediate section.

References Cited by the Examiner t UNITED STATES PATENTS 1,394,119 10/1921 Rockwell 16138 1,791,422 2/1931 McVay 22915 2,046,985 7/ 1936 Wilkins 229-28 2,328,454 8/1943 Horvath 161-1 13 2,511,620 6/ 1950 Clements 49--503 2,893,076 7/1957 Herts 52615 X 3,070,198 12/1962 Haskell 52666 X 3,082,142 3/1963 Payne 161-68 3,101,652 8/ 1963 Imielinski 229--28 3,109,766 12/1'963 Norris 161-68 FOREIGN PATENTS 649,968 1962 Canada.

610,451 1948 Great Britain.

RICHARD W. COOKE, JR., Primary Examiner.

JOHN E. MURTAGH, FRANK ABBOTT, Examiners. 

1. IN COMBINATION, A FRAME HAVING A PRESELECTED WIDTH AND A HOLLOW LADER-TYPE CORE DISPOSED IN SAID FRAME, SAID CORE COMPRISING A PLURALITY OF STRIPS OF CORRUGATED PAPER BOARD PRESELECTED ONES OF WHICH HAVE A WIDTH SUBSTANTIALLY EQUAL TO SAID PRESELECTED WIDTH, AND HINGE-LIKE HOLDING MEANS AT THE ENDS OF THE STRIPS FOR HOLDING EACH STRIP TO AN ADJACENT STRIP TO FORM A SINGLE CELL WHICH EXTENDS BETWEEN THE BOUNDARIES OF SAID FRAME, SAID HINGE-LIKE HOLDING MEANS COMPRISING CONNECTING PIECES CONNECTED BETWEEN ADJACENT ONES OF STRIPS OF CORRUGATED PAPER BOARD AND BEING FOLDABLE ALONG SAID CONNECTIONS, EACH OF SAID CONNECTING PIECES HAVING A FOLD LINE INTERMEIDIATE SAID CONNECTIONS WHEREBY EACH CONNECTING PIECES IS FOLDABLE ALONG ITS LINES OF CONNECTION TO ADJACENT ONES OF SAID STRIP AND ALONG SAID INTERMEDIATE FOLD LINE, SAID CONNECTING PIECES BEING FORMED OF A METERIAL THAT IS THE SAME AS THE CORRUGATED PAPER BOARD. 